1. Technical Field
The present invention relates to a liquid ejecting head that is provided with a substrate on which wiring that penetrates through a plate thickness direction, is formed, and a manufacturing method of a liquid ejecting head.
2. Related Art
A liquid ejecting apparatus is an apparatus that is provided with a liquid ejecting head, and that ejects various liquids from the liquid ejecting head. Image recording apparatuses such as ink jet printers and ink jet projectors are examples of such liquid ejecting apparatuses, but in recent years, liquid ejecting apparatuses have also been applied to various manufacturing apparatuses to make use of the feature of being able to accurately land a very small quantity of liquid in a predetermined position. For example, liquid ejecting apparatuses have been applied to display manufacturing apparatuses that manufacture color filters such as liquid crystal displays, electrode formation apparatuses that form electrodes such as organic Electro Luminescence (EL) displays and Field Emitting Displays (FEDs), and chip manufacturing apparatuses that manufacture biochips (biochemical elements). Further, liquid form ink is ejected in recording heads for image recording apparatuses, and solutions of each color material of Red (R), Green (G), and blue (B) are ejected in color material ejecting heads for display manufacturing apparatuses. In addition, liquid form electrode materials are ejected in electrode material ejecting heads for electrode formation apparatuses, and solutions of living organic material are ejected in living organic material ejecting heads for chip manufacturing apparatuses.
In the abovementioned liquid ejecting heads, a pressure chamber formation substrate on which a pressure chamber that is in communication with a nozzle, is formed, a piezoelectric element (a kind of actuator) that brings about a pressure fluctuation in liquid inside the pressure chamber, a sealing plate (also referred to as an interposer board) in which a gap is opened and disposed to correspond to the corresponding piezoelectric element, and the like are laminated. Further, the above-mentioned piezoelectric element is driven by a driving signal that is supplied from a driving IC (also referred to as a driver IC). This kind of driving IC is installed in a Tape Carrier Package (TCP) which is connected to an upper surface (a surface that is on an opposite side to a piezoelectric element) of a sealing plate, or is directly installed on the upper surface of the sealing plate, and supplies a driving signal to the piezoelectric element through wiring that is formed on the sealing plate. The wiring that relays between the driving IC and the piezoelectric element is configured from outer surface wiring that is formed on the upper surface and the lower surface of the sealing plate, penetration wiring that is formed inside a penetration hole and penetrates through the sealing plate, and the like (for example, JP-A-2012-126028).
Incidentally, for example, a method that grows a conductor (a metal) inside a penetration hole, in which an adhesive layer (a seed layer), which improves adhesive properties with a conductor, is formed as a film, using an electrolytic plating technique by forming the adhesive layer as a film inside the penetration hole using a sputtering technique or the like, is an example of a method that forms penetration wiring inside the penetration hole of the above-mentioned sealing plate. However, in accordance with the miniaturization of liquid ejecting heads, when the internal diameter of the penetration hole is reduced, and the aspect ratio (a ratio of the length L of the penetration hole (or the substrate thickness) with respect to the opening diameter D of the penetration hole, that is, L/D) of the penetration hole is increased, it is difficult to form the adhesive layer in an inner portion of the penetration hole. Therefore, a sputtering technique that can form an adhesive layer having a favorable coverage (covering) ratio up to the inner portion, in even a penetration hole having a comparatively large aspect ratio, was developed (refer to JP-A-2012-111996).
As the miniaturization of liquid ejecting heads continues, and aspect ratios of penetration holes are further increased, there is a concern that it will not be possible to form a sufficient adhesive layer even using the method that is disclosed in JP-A-2012-111996. That is, there is a concern that the coverage (covering) ratio of the adhesive layer in the inner portion inside the penetration hole will deteriorate. As a result of this, when the adhesive properties of a conductor, which is formed inside the penetration hole, and the inner wall of the penetration hole deteriorate, and heat is applied due to a subsequent manufacturing process, a specification environment of a product, or the like, there is a concern that the conductor inside the penetration hole will stick out (protrude), or will slip out, to an outer side from the penetration hole due to a difference in the thermal expansion coefficients of the sealing plate and the conductor. In addition, even supposing it is possible to form an adhesive layer inside the penetration hole, when the difference between the thermal expansions of the sealing plate and the conductor is large, there is a concern that sticking out, or slipping out of the conductor will occur.